How does a rectangular sunchart change with latitude?

Thomas M Crawford
8/3/2009

Purpose

The purpose of this page is to allow you to observe the evolution of the rectangular sunchart as the latitude is changed. This page shows a series of suncharts starting at the equator, and then stepping northward in 10 degree steps. Scroll down the page to observe how the sunchart evolves with latitude. For a similar page showing the evolution of the polar sunchart with latitude, go to: How does a polar sunchart change with latitude?

Return to: Using a sunchart for solar design.

Rectangular sunchart for 0 degrees north latitude. This sunchart represents what you would see if you were standing on the equator looking south. It seems a little confusing. Just remember, half the year the sun spends all its time south or in front of you, and half the year the sun spends all its time north or behind you. Only one day in March (approximately 3/21) and one day in September (approximately 9/21) does the sun rise exactly in the east, pass directly overhead, and set exactly in the west. To get a better idea of what the sun is doing when you stand on the equator, take a look at the corresponding polar sunchart. When the sun is high in the sky, such as in the tropics (near the equator), I find a polar sunchart a much better view of reality than the rectangular sunchart.

Rectangular sunchart for 10 degrees north latitude. The view from this sunchart is from 10 degrees north of the equator. This location is well within the tropics and is south of the Tropic of Cancer. The sun passes south of this location most of the year, but there are a few months that the sun passes behind or north of a south facing observer. Again the rectangular sunchart is more confusing than the polar sunchart, especially for the summer months when the sun is passing north of this latitude.

Rectangular sunchart for 20 degrees north latitude. The view from this sunchart is from 20 degrees north of the equator. This location is just south of the Tropic of Cancer, so the sun still travels north of an observer during parts of May, all of June, and parts of July.

Rectangular sunchart for 30 degrees north latitude. The view from this sunchart is from 30 degrees north of the equator. The location of this observer is well north of the Tropic of Cancer, so the sun will always pass south of this observer at solar noon. The sun does rise north of east and set north of wes during summer months.

Rectangular sunchart for 40 degrees north latitude. The view from this sunchart is from 40 degrees north of the equator. Notice how the days get longer in the summer and shorter in the winter the further north you go.

Rectangular sunchart for 50 degrees north latitude. The view from this sunchart is from 50 degrees north of the equator. Again notice how the days continue to get longer in the summer and shorter in the winter the further north you go.

Rectangular sunchart for 60 degrees north latitude. The view from this sunchart is from 60 degrees north of the equator. This location is still south of the Arctic Circle, but the days are very long (~18 hours) in the summer and very short in the winter (~6 hours).

Rectangular sunchart for 70 degrees north latitude. The view from this sunchart is from 70 degrees north of the equator. This is our first sunchart north of the Arctic Circle. The sun never sets during certain months of the summer (parts of May, all of June, parts of July), and the sun never rises during certain parts of the winter (parts of November, all of December, parts of January). During the months the sun does not set, the sun goes clear around the sky, but never get very high in the sky. Since the sun never sets at this time, we experience the "Midnight Sun" at which time the sun is due north of the observer (solar midnight).

Rectangular sunchart for 80 degrees north latitude. The view from this sunchart is from 80 degrees north of the equator. We are now well north of the Arctic Circle. The sun never sets during certain after sometime in April until near the end of August.

I have not plotted a sunchart for the North Pole, but it would look like a series of parallel lines since the sun will rotate clear around the sky during the spring and summer months and will slowly creep up the sky during the spring, while slowly creep down the sky during the summer. The sun first appears during the first day of spring, and sets during the first day of fall.